Crystal amplifier



March 23, 1954 s. F. AMICO CRYSTAL AMPLIFIER Filed July 24, 1948 R Mm m T AM E w Q T O m 1 Q S Patented Mar. 23, 1954 CRYSTAL AMPLIFIER Salvatore F. Amico, East Boston, Mass., assignor to Sylvania. Electric Products Inc., Salem, Mass., a corporation of Massachusetts Application July 24, 1948, Serial No. 40,561

8 Claims.

- This invention relates to semi-conductors such as crystals and the like, and to securing amplification and the like with such devices by adding an additional or control contact. Such devices have come to be known as transistors.

My invention provides an efiective structure for a crystal unit giving amplification. A feature of the invention is a pair of twin catwhiskers, or wire contacts, separated by an insulating piece. Other features are a simple cartridge type structure.

Other objects, features and advantages of this invention will be apparent from the following specification and its accompanying drawings, in which:

Figure 1 is a view, partly broken away for clarity, of a device according to the invention; and

Figure 2 is another view of a pair of contacts for such a device.

In the figures, the crystal I, which may be for example of germanium containing a small amount, say 0.1% of tin as an activating impurity, is fixed to the metal disc 2 by the solder 3, in which a pig-tail lead-in wire d is also affixed.

The catwiskers 5 and 6 are arranged on pposite sides of a mica or other insulating sheet I. The catwiszers 5, 6 may have conically pointed ends 8, 9 in contact with the surface of crystal i on the crystal side opposite that which rests on the metal disc 2. The other ends of the catwhiskers may be connected to the nickel pieces or pins ll, i2 which pass through a plastic bead or disc l3, the mica I also passing through said. disc l3. Pig tail lead-in wires M, may be soldered to the ends of pins H, l2, and a metal cylinder [6 may enclose the device and support its discs l3, 2 in their proper position. The pig-tail lead-in wires 4, l5, it are shown covered by insulating tubes l7, l8, [9 if desired, although this is not necessary.

The catwhiskers 5, 6 may be made as shown in copending application, Serial No. 492,163, now Patent No. 2,572,801, filed June 23, 1943 by E. T. Casellini, for example. They may be 0.005 inch in diameter for example, with their points machined to true right circular conical points. In some cases, the wires may be machined to a single point, as in Figure 2, having two insulated halves 20, 2| and each is advantageously so shaped and of such material as to bear resiliently with desired pressure against the crystal, for example tungsten and of S-shaped contour, as more fully described in the foregoing Casellini application.

In one embodiment of the invention the plastic bead It! was of 0.186 inch diameter and VB inch depth. The wires 5, 6 were passed through an approximate one-sixteenth inch hole 22 in head [3 after a 0.001 inch piece of mica had been placed between them for insulation and spacing.

The assembly is such that the points 8, 9 of the two wires 5, B are within about 0.002 inch of each other in a plane perpendicular to the wire axis, with one point no more than about 0.001 inch above the other, measured along the axis of the wires 5, 6. The points may be brought into alignment, if necessary, by bending the whisker ends. With the wire diameter shown and right cone circular points on each, one of the points will have to be bent toward the other to secure proper spacing; with the points of Fi ure 2 this need not be necessary.

The plastic bead I3 with its wires 5, 6, mica l and other elements, is inserted by a force fit into a slightly undersized, 0.185 inch inside diameter and 2; inch long in the embodiment decribed, cartridge [6 the top of the bead I3 being placed about inch below the top of the cartridge i6. bead It may be filled with cement (not shown, for convenience) such as Alundum in nitrocellulose or a plastic cement. Into the other end of the cartridge I6 is inserted a metal plug 2, to which has been soldered a crystal I, for example of germanium. The plug 2 is slightly oversize with respect to the internal diameter of cartridge I6, into which it is forced until contact is made with the points 8, 9 and is advanced until the catwhisker tension is such as to give suitable resistance in the main current-carrying direction. This may be about 200 ohms at 1 volt direct current.

Each contact is then treated to short electrical pulses of say, 5 to 25 volts alternating current through a current-limiting resistance, for example, 10 ohms until the electrical characteristics are such as to be expected with the crystal I used. The unit should be checked to insure that there are no short circuits.

Germanium crystals giving very high amplification have been made.

The catwhiskers 5, 6 may be of any suitable metal for example tungsten or nickel. The catwhiskers 5, 6 are shown with their loops in the same position, but the loops may be reversed if desired.

Before contact is made to the crystal surface, the latter may be suitably polished and etched to give proper electrical characteristics, for ex- The top of the cartridge I6 above 1 ample being polished with 4/0 emery paper and oil polish and chemically etched.

An amplification factor of about 200 has been obtained with a crystal of this type.

What I claim is:

1. A semi-conductor crystal unit comprising a semi-conductor crystal, a back contact thereto, and two catwhisker contacts thereon, and an insulating plate separating the catwhiskers by a distance of the order of 0.002 inch.

2. A semi-conductor crystal unit comprising a semi-conductor crystal, a back contact thereto, and two catwhisker contacts thereto, said contacts comprising wires bent to have oppositely extending loops in parallel planes, and a sheet of insulating material between said wires and in lengthwise contact therewith.

3. The combination of claim 2, a plastic plug carrying the insulating sheet and one end of each of said wires, and being fitted into an outer metal cartridge, and a metal plug afiixed to said crystal and fitted into said. cartridge to bring said wires into contact with the crystal.

4. A semiconductor unit including a semiconductor element, a back contact thereto, and multiple sharp contacts thereon, said sharp contacts being at the end of a pair of resilient wires, a plate of insulation between the contact wires, and an insulating support receiving said wires and said insulating plate and holding the wires so as to lie laterally against the insulating plate.

5. A semiconductor crystal unit of the sharpcontact transistor type, including a semiconductor crystal, a back contact thereto, and two catwhisker contacts thereon, a thin insulating plate between said catwhisker contacts extending in close proximity to said crystal, and means holding the catwhisker contacts laterally against said insulating plate, said insulating plate thereby servin to separate the catwisker contacts by a distance substantially equal to the thickness of the insulating plate.

6. A semiconductor crystal unit of the sharpcontact transistor type, including a semiconductor crystal, a back contact thereto, two sharp contacts separately supported and engaging said crystal independently of each other, and a layer of insulation interposed between said sharp contacts extending close to said crystal serving to fix the separation of said sharp contacts at a small distance.

7. A semiconductor crystal unit of the sharpcontact transistor type, including a semiconductor crystal, a back contact thereto, two sharp contacts thereon having separate biasing means for independently developing pressure of the contacts individually against the crystal, and a predetermined thickness of insulation extending in close proximity to but spaced from the crystal and interposed between and laterally engaging said sharp contacts and serving to fix the separation between the sharp contacts at a small distance.

8. A semiconductor device comprising a semiconducting body, two metallic electrodes in rectitying contact with said body, said rectifying electrodes having substantially point like contact with said body, a further electrode in low resistance contact with said body, and insulation between said electrodes close to their contact with said body but spaced from said body and having a thickness for spacing said rectifying electrodes apart a predetermined small distance.

SALVATORE F. AMIGO.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 2,156,660 Van Geel May 2, 1939 2,378,944 Ohl June 26, 1945 2,438,110 Brattain Mar. 23, 1948 2,486,776 Barney Nov. 1, 1949 2,524,033 Bardeen Oct. 3, 1950 2,524,035 Bardeen et al. Oct. 3, 1950 

